The present invention relates to an arrangement in hearing protection devices, head phones and the like, comprising a generally U-shaped frame having plugs at its both ends, which plugs by the frame are pressed into contact with the orifices of the auditory meatus.
While the invention will below be described in connection with a hearing protection device, it may also, as mentioned above, be utilized e.g. in connection with head phones and the like suffering from problems similar to those occurring in hearing protection devices and accounted for below.
A most widely used type of hearing protection device consists of a U-shaped frame, at each of its two ends equipped with soft plugs which by the frame are pressed into sealing engagement with the orifices of the auditory meatus. The plugs may be shaped so that a portion thereof slightly enters the passage. In order to match the irregular shape of the passage the plugs are generally manufactured in a soft rubber or plastic material. The frame generally consists of a relatively stiff plastic material in order to create a suitable, resilient force pressing against the plugs in order to attain an efficient sealing between each of them and related passage orifices. In this way one achieves a good damping of sounds from ambient noise sources.
However, this type of hearing protection device suffers from a disadvantage in that the frame may itself generate undesired noise, namely if hit by or brought into rubbing contact with another object. As the frame is usually located under the chin or around the back of the head this may occur at movements of the head causing e.g. a necklace to hit the frame or the frame to just scrape along an article of clothing, e.g. a shirt collar.
When the frame is affected mechanically, vibrations are generated therein, i.a. in the form of axial oscillations in the direction of the adjacent plug. Because of the soft material in the plug those oscillations are not dampened to any appreciable extent. While the amplitude of the frame and plug movements is small they will, i.a. in consequence of the small volume of air between the plug and the tympanic membrane, result in sound-generating pressure variations in the hearing passage which cause sound pressure.